You have to improvise a bit to get a VTEC sound close to reality.

I took a turbo engine. Edited the power delivery with new tweak order and lfs tweak. Torque and power can be used to initiate the building of boost (Highest torque and highest power should be near to each other). Just try to find a point where boost is build up rapidly (will be your VTEC crossover point). Turbo response should be set to 0.01. Now go the engine sound menu and save the normal air intake sound (should be one you like and can also be the ai sound from another car). Afterwards load the air intake sound for or better instead of the normal turbo sound. Turn off the blow off sound. When the boost comes on, you will have a 2nd intake sound the gets very loud immediately (also depends on boost level). Voila, there is your VTEC sound. A bit of work and you have to try a lot of settings, but you will get there

I had a B16A Honda in former times, so I had to make such a sound